Fair Value (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 2,099.1		$ 3,796.0
Short-term investments	6.7		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.3		1.0
Investment in equity securities without readily determinable fair value	11.8		14.4
Liabilities:
Short-term debt	11.3		11.8
Interest rate and foreign currency derivative instruments	83.5		39.5
Contingent purchase price obligations	225.0		215.6
Long-term debt, including current portion	4,840.3		5,056.9
Carrying Amount
Assets:
Cash and cash equivalents	2,099.1		3,796.0
Short-term investments	6.7		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.3		1.0
Investment in equity securities without readily determinable fair value	11.8		14.4
Liabilities:
Short-term debt	11.3		11.8
Interest rate and foreign currency derivative instruments	83.5		39.5
Contingent purchase price obligations	225.0		215.6
Long-term debt, including current portion	4,857.2		4,912.9
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	215.6	$ 386.1
Acquisitions	84.1	41.7
Revaluation and interest	8.7	0.2
Payments	(66.4)	(182.9)
Foreign currency translation	(17.0)	15.9
September 30	225.0	$ 261.0
Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	2,099.1		3,796.0
Short-term investments	6.7		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.3		1.0
Liabilities:
Interest rate and foreign currency derivative instruments	83.5		39.5
Contingent purchase price obligations	225.0		215.6
Fair Value, Measurements, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	2,099.1		3,796.0
Short-term investments	6.7		0.4
Investment in equity securities	1.6		1.4
Fair Value, Measurements, Recurring [Member] | Level 2
Assets:
Foreign currency derivative instruments	0.3		1.0
Liabilities:
Interest rate and foreign currency derivative instruments	83.5		39.5
Fair Value, Measurements, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 225.0		$ 215.6